Laundry dryers generally comprise a casing that houses a laundry container, like a rotating drum, where laundry to be treated is received, and an air circuit for carrying out drying operation by circulating hot air through the laundry container. In a heat pump laundry dryer, drying air coming out from the laundry container is first dehumidified through a first heat exchanging portion (a refrigerant fluid evaporating unit) of a heat pump circuit, and then heated through a second heat exchanging portion (a refrigerant fluid condensing unit) of the same heat pump circuit thereby achieving a considerable energy saving compared to a condenser type laundry dryer. In the latter type of laundry dryer, condensing means in the form of an air-air heat exchanger are provided in the drying air circuit for removing moisture from laundry drying air while heat is generated by an electric resistance placed within the drying air circuit.
Both in heat pump and in condenser dryers moisture removed from drying air is collected within a reservoir located in the cabinet bottom part and then pumped up to a removable container placed on a front upper portion of the cabinet by pumping means. Since condensed moisture is drained from the drying air circuit, in prior art dryers part of such air may be drained together with moisture and being sucked into said pumping means thereby causing damages and/or a malfunction of the draining system.
In addition, even when filtered, drying air may comprise fluff particles that can cause pump clogging in case an amount of drying air mixes with condensed moisture. Fluff accumulated on those parts of the drying air circuit just downstream of the main air filter, which is generally provided in proximity of an air outlet port in the laundry container, may be flushed away by moisture contained in drying air when the latter passes through cold surfaces. This problem may arise especially after a relatively large number of cycles or when drying air filters and/or condensing devices are not periodically cleaned.
Furthermore, prior art laundry dryers generally provides draining arrangements in correspondence of elements, such as an evaporator in a heat pump type dryer or a condenser in a condenser type dryer, where moisture is effectively condensed but such dryers have no provision for collecting condensate in other regions of the drying air circuit where temperature may be favorable to moisture condensation. In a laundry dryer of heat pump type, one of the above said regions has been found to be the heat exchanger (a refrigerant fluid condensing unit) provided for heating the drying air flow. This is due to the fact that, in a heat pump type dryer, the position of the condensing unit is quite near to that of the cold surfaces of the evaporating unit and therefore moisture can be further condensed on a region of the condensing unit adjacent to the evaporating unit. Presence of condensate on a heat pump circuit condenser is particularly undesired because the condensing unit yield drops dramatically.
In a heat pump type dryer, a further potential moisture condensing surface may be the region in front of the evaporating unit, i.e. a region upstream of such unit considering the flow direction of laundry drying air, because the drying air enters that region with the highest amount of humidity with respect to the whole drying air circuit. Since that region may feel the evaporator low temperature, a moisture condensation becomes highly probable. In addition, in said region facing the evaporator unit, drying air flow changes its direction from a substantially vertical plane to a substantially horizontal plane. This causes air to contact drying air conduit walls thereby increasing possibility for a moisture condensation on such walls. A moisture condensation in that region may disadvantageously cause undesired and uncontrolled water shedding.